The present invention relates to an electronic imaging apparatus having a CCD image sensor, that is, a so-called electronic still camera.
Recently, research and development of electronic imaging apparatuses capable of inputting image data to multimedia equipment, so-called electronic still cameras have energetically been performed. In general, the electronic still camera obtains an image by using a CCD image sensor to display the obtained image on an electronic view finder, such as a liquid crystal panel, and to record the image on a recording medium by, for example, a magnetic means in accordance with depression of the trigger performed by a user.
Although the electronic still camera is a very easy device to use because no development of film is required, further improvement in the image quality and case of have been required of the electronic still camera. To satisfy the foregoing requirements, an image having the same angle of views which is the same as that of the image which must be photographed is required to be observed in real time through an electronic view finder, and a CCD image sensor having a large number of pixels must be used.
CCD image sensors having the number of effective pixels, which is larger than 1,000,000, have been realized. It is considered that CCD image sensors having larger pixels will be put into practical use. CCD image sensors arranged to photograph a still image and adapted to sequential scanning for sequentially, reading image signals for each line have been used in place of the conventional interlaced scanning. The reason for this lies in that prevention of deterioration in the image quality attributable to the difference in time required to read pixel signals from adjacent lines has been attempted.
The main stream of the operation clock frequencies of marketed A/D converters is about 15 MHz to about 20 MHz. When also reduction in the electric power consumption is attempted, higher drive frequencies are detrimental to the improvement. Frame rates of about 10 to 15 frames/second can be realized by the sequential scanning operation of CCD image sensors of 1,000,000-pixel class.
With the above-mentioned degree of the frame rate, the displayed image is recognized by the human eyes as a pseudo dynamic image (or motion picture) realized by frame advance in place of being recognized as a natural image. To display an image as a natural image for the human eyes, a frame rate of 30 to 60 frames/second is required.
An object of the present invention is to provide an electronic imaging apparatus having a large number of pixels, for example, 1,000,000 pixels, and which is capable of displaying an image which is recognized as a dynamic image in a non-photographing mode even with a relatively low operation frequency, for example, 20 MHz or lower.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained particularly pointed out in the appended claims.